1. Field of the Invention
The present invention relates to a material composition and its use for the packaging of light-sensitive components.
2. Description of the Prior Art
In view of the coming of digital age, light-sensitive components have been widely utilized in various electronic products. Particularly, the development of image sensors has progressed rapidly.
In general, a method for packaging an image sensor comprises using a mold compound to form a dam around each modular circuit by a transfer molding process; fixing an image sensor to the circuit by a conductive adhesive and accomplishing the wire bonding; applying an adhesive over the dam and placing a glass sheet on the adhesive; and curing the adhesive. ROC Patent Publications No. 459355, 478136, 503574, and 501244 have disclosed packaging structures and methods of image sensors.
In conventional processes, the light-transmission layer covering image sensor chips is normally glass, as disclosed in the above-mentioned patent publications. This is because glass has low refractive indices, high light-transmission, and scratch resistance. However, in the processes utilizing light-transmission layers of glass, the chips can only be packaged one by one. Such packaging manner will consume a larger amount of efforts and time, cannot achieve good yields, and is costly.
ROC Patent Publication No. 489532 describes a stacked structure of an image sensor. This patent publication also discloses utilizing a molding compound and transfer molding, but the light-transmission layer for covering by molding is a transparent resin layer rather than a glass sheet, Nonetheless, said patent publication does not teach, disclose, or suggest what the properties which the resin would possess are or what the effects which the resin would have on light are.
Although conventional epoxy resins with a benzene ring, such as bisphenol A epoxy resin, bisphenol F epoxy resin, and nathalene-type epoxy resin, are transparent, the refractive indices of such resins upon curing are all higher than 1.50. This is because when the visible light passes through a benzene ring, the unsaturated π bond of the benzene ring will absorb the light to reduce a π−π* interaction and to alter the refractive indices and the light transmission rates. The use of those epoxy resins without any benzene rings may effectively reduce refractive indices. However, such resins do not have the properties, such as high glass transition temperatures and heat resistance, that glass possesses.
The inventors of the subject application have found that there are certain material compositions that are useful as encapsulating materials for packaging, in particular, the packaging of image sensors. Such material compositions, after being cured, will provide the advantages of high glass transition temperatures, low refractive indices, high light transmission, and scratch resistance, and can be used in transparent layers and as substitutes for glass. When utilizing the compositions of the present invention for packaging on a substrate, said compositions may be cured by heat and then the packaged substrate can be divided into single modules. Such packaging manner is simpler than that for single chip when using glass, and will reduce production cost and enhance production capacity and yield.